Printed circuit board and method of fabricating the same

ABSTRACT

A printed circuit board includes an insulating layer, a circuit pattern on the insulating layer, and a surface treatment layer on the circuit pattern. The surface treatment layer includes a bottom surface having a width wider than a width of a top surface of the circuit pattern.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.17/653,054, filed Mar. 1, 2022; which is a continuation of U.S.application Ser. No. 17/236,519, filed Apr. 21, 2021, now U.S. Pat. No.11,297,720, issued Apr. 5, 2022; which is a continuation of U.S.application Ser. No. 17/005,522, filed Aug. 28, 2020, now U.S. Pat. No.11,019,731, issued May 25, 2021; which is a continuation of U.S.application Ser. No. 16/717,679, filed Dec. 17, 2019, now U.S. Pat. No.10,798,827, issued Oct. 6, 2020; which is a continuation of U.S.application Ser. No. 15/878,701, filed Jan. 24, 2018, now U.S. Pat. No.10,531,569, issued Jan. 7, 2020; which is a continuation of U.S.application Ser. No. 15/594,778, filed May 15, 2017, now U.S. Pat. No.9,913,383, issued Mar. 6, 2018; which is a continuation of U.S.application Ser. No. 14/831,674, filed Aug. 20, 2015, now U.S. Pat. No.9,686,860, issued Jun. 20, 2017; which claims the benefit under 35U.S.C. § 119 to Korean Patent Application No. 10-2015-0100404, filedJul. 15, 2015; all of which are hereby incorporated in their entirety.

BACKGROUND

The disclosure relates to a printed circuit board, and more particularlyto a printed circuit board, which includes a circuit pattern having acurved surface in a portion of a lateral side thereof and a surfacetreatment layer formed through electrolytic plating, and a method offabricating the same.

A printed circuit board (PCB), which is formed by printing a circuitline pattern on an electrically insulating substrate using a conductivematerial, such as copper (Cu), signifies a board immediately beforeelectronic components are mounted thereon. That is to say, the PCBsignifies a circuit board in which the mounting positions of theelectronic components are determined, and circuit patterns are printedon and fixed to the surface of a flat plate to connect the electroniccomponents with each other, in order to densely mount various types ofelectronic devices on the flat plate.

In general, for the surface treatment of the circuit patterns formed onthe PCB, Organic Solderability Preservative (OSP) has been used, andelectrolytic nickel/gold, electrolytic nickel/gold-cobalt alloy, orelectroless nickel/palladium/gold has been used.

In this case, various surface treatment schemes may be employedaccording to the use purposes thereof. For example, the surfacetreatment schemes for soldering, wire-bonding, and a connector may beused.

FIGS. 1(a) and 1(b) are sectional views showing a PCB according to therelated art.

Referring to FIGS. 1(a) and 1(b), the PCB includes an insulating layer10, a plating seed layer 20, a circuit pattern 30, a protective layer40, a first surface treatment layer 50, and a second surface treatmentlayer 60.

FIGS. 1(a) and 1(b) show the insulating layer 10, the plating seed layer20, the circuit pattern 30, the first surface treatment layer 50, andthe second surface treatment layer 60 having the same structures exceptfor protective layers 40 having different structures according to theused shape thereof.

In other words, the protective layer 40 shown in FIG. 1(a) covers theentire exposed surface of the insulating layer 10 while covering atleast a portion of a top surface of the circuit pattern 30, and has ashape of protruding upward from the surface of the second surfacetreatment layer 60.

The protective layer 40 shown in FIG. 1(b) serves only as an embankment.Accordingly, the protective layer 40 exposes at least a portion of thesurface of the insulating layer 10 in the state that the protectivelayer 40 does not make contact with the circuit pattern 30.

Meanwhile, the above PCB according to the related art includes the firstsurface treatment layer 50 including nickel (Ni) and the second surfacetreatment layer 60 including gold (Au) for the surface treatment of thecircuit pattern 30.

In this case, the first surface treatment layer 50 and the secondsurface treatment layer 60 are generally formed through electrolessplating since a seed layer for electroplating does not separately exist.

In addition, to form the first and second surface treatment layers 50and 60 through the electrolytic plating, a plating seed layer must beadditionally formed.

However, design limitations may exist as the additional seed layer isformed in order to perform the electroplating even though the surfacetreatment of the PCB is generally performed through the electrolessplating.

In addition, the surface treatment of the PCB essentially requires theformation of the first surface treatment layer 50 including metal, suchas Ni, for the diffusion of the circuit pattern 30 including Cu.

SUMMARY

The embodiment of the disclosure provides a printed circuit board havinga surface treatment layer of a circuit pattern formed throughelectroplating using a plating seed layer used when the circuit patternis formed, and a method of fabricating the same.

The embodiment of the disclosure provides a printed circuit board, whichincludes a circuit pattern having a curved surface in at least a portionof a lateral side thereof, and a method of fabricating the same.

The embodiment of the disclosure provides a printed circuit board, whichincludes a surface treatment layer formed on a circuit pattern andhaving a width narrower than that of a bottom surface of the circuitpattern and wider than that of a top surface of the circuit pattern, anda method of fabricating the same.

Technical objects of the embodiment may not be limited to the aboveobject and other technical objects of the embodiment will be apparent tothose skilled in the art from the following description.

According to the embodiment, there is provided a printed circuit boardincluding an insulating layer, a circuit pattern on the insulatinglayer, and a surface treatment layer on the circuit pattern. The surfacetreatment layer includes a bottom surface having a width wider than awidth of a top surface of the circuit pattern.

Further, in the circuit pattern, at least one of an upper right lateralside and an upper left lateral side thereof has a predeterminedcurvature.

In addition, the width of the top surface of the circuit pattern isnarrower than a width of a bottom surface of the circuit pattern, andthe bottom surface of the circuit pattern includes a first areavertically overlapped with the top surface of the circuit pattern and asecond area except for the first area.

In addition, the surface treatment layer includes a gold (Au) surfacetreatment layer including a metallic material including gold (Au), and abottom surface of the gold (Au) surface treatment layer directly makescontact with the top surface of the circuit pattern.

The bottom surface of the surface treatment layer has a width narrowerthan a width of a bottom surface of the circuit pattern.

Further, the surface treatment layer includes a contact area makingcontact with the top surface of the circuit pattern and a non-contactarea that does not make contact with the top surface of the circuitpattern, the second area of the circuit pattern includes a third areathat is not vertically overlapped with the non-contact area of thesurface treatment layer and a fourth area vertically overlapped with thenon-contact area of the surface treatment layer, and the third area hasa width wider than a width of the fourth area.

In addition, the width of the third area to the width of the fourth areasatisfies a range of 1.5 to 4.0.

Further, a plating seed layer interposed between the insulating layerand the circuit pattern is additionally included, and the plating seedlayer serves as a seed layer for the circuit pattern and the surfacetreatment layer.

In addition at least one of a left lateral side and a right lateral sideof the circuit pattern includes a first portion substantiallyperpendicular to a bottom surface of the circuit pattern and a secondportion extending from the first part and having a curved surface with apredetermined curvature.

In addition, a left area or a right area of the surface treatment layerprotrudes outward from an upper left lateral side or an upper rightlateral side of the circuit pattern, respectively.

Further, a protective layer formed on the insulating layer isadditionally included to cover at least a portion of a surface of theinsulating layer.

Meanwhile, according to the embodiment, there is provided a method offabricating a printed circuit board. The method includes preparing aninsulating layer formed on a top surface thereof with a plating seedlayer, forming a circuit pattern on the insulating layer by performingelectroplating with respect to the plating seed layer serving as a seedlayer, forming a mask, which has an opening, on the plating seed layerto expose at least a portion of a top surface of the circuit pattern,forming a surface treatment layer on the circuit pattern by performingelectroplating with respect to the plating seed layer serving as theseed layer such that the surface treatment layer is filled in at least aportion of the opening, removing the mask from the plating seed layer,and removing the plating seed layer from the insulating layer.

The mask includes a dry film.

In addition, the opening of the mask has a width narrower than a widthof the top surface of the circuit pattern, and the at least portion ofthe top surface of the circuit pattern is covered by the mask.

In addition, the circuit pattern, which exists before the plating seedlayer is removed, comprises a first top surface making contact with abottom surface of the surface treatment layer and a second top surfacethat does not make contact with the bottom surface of the surfacetreatment layer, and a portion of the second top surface of the circuitpattern is removed together with the plating seed layer when the platingseed layer is removed.

In addition, the circuit pattern, which exists after the plating seedlayer is removed, includes the top surface having the width narrowerthan a width of the bottom surface of the surface treatment layer

In addition, the circuit pattern, which exists after the plating seedlayer is removed, has a lateral side extending from the second topsurface and having a predetermined curvature.

Further, the surface treatment layer comprises a gold (Au) surfacetreatment layer including a metallic material including gold (Au), and abottom surface of the gold (Au) surface treatment layer directly makescontact with the top surface of the circuit pattern.

In addition, the bottom surface of the surface treatment layer has awidth narrower than that of the bottom surface of the circuit pattern.

Further, a step of forming a protective layer on the insulating layer tocover at least a portion of a surface of the insulating layer is furtherincluded.

According to the embodiment of the disclosure, the surface treatmentlayer is formed by utilizing a removable film-type material and aplating seed layer used in the circuit pattern, so that the electrolyticsurface treatment and the electroless surface treatment can beselectively used without the limitation on the design.

According to the embodiment of the disclosure, the surface treatmentlayer including Au is formed using the plating seed layer used when thecircuit pattern is formed, so that the conventional Ni surface treatmentlayer serving as a seed layer for the Au surface treatment layer can beomitted. Accordingly, the thickness of a product can be reduced, andproduct cost can be reduced due to the omission of the Ni surfacetreatment layer.

In addition, according to the embodiment of the disclosure, theconventional nickel (Ni) surface treatment layer can be omitted, and thesurface treatment layer including gold (Au) can be formed directly onthe circuit pattern, thereby increasing the electrical conductivity, andreducing the electrical resistance. Accordingly, the RF characteristicmay be improved.

In addition, according to the embodiment of the disclosure, the surfacetreatment layer formed on the circuit pattern has an eave structure ofprotruding outward from the upper lateral side of the circuit pattern,so that the mounting area of the components mounted on the circuitpattern can be increased. Accordingly, the reliability of a customer canbe improved.

The details of one or more embodiments are set forth in the accompanyingdrawings and the description below. Other features will be apparent fromthe description and drawings, and from the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1(a) and 1(b) are sectional views showing a printed circuit boardaccording to the related art.

FIG. 2 is a sectional view showing the structure of a printed circuitboard according to the first embodiment of the disclosure.

FIG. 3 is a sectional view showing the circuit pattern of FIG. 2 indetail.

FIGS. 4 to 11 are sectional views showing a method of fabricating theprinted circuit board of FIG. 2 in process sequence.

FIG. 12 is a sectional view showing the structure of a printed circuitboard according to the second embodiment of the disclosure.

FIGS. 13 to 15 are sectional views showing a method of fabricating theprinted circuit board of FIG. 12 .

FIG. 16 is a sectional view showing the structure of a printed circuitboard according to the third embodiment of the disclosure.

FIG. 17 is a sectional view showing the structure of a printed circuitboard according to the fourth embodiment of the disclosure.

FIG. 18 is a sectional view showing the structure of a printed circuitboard according to the fifth embodiment of the disclosure.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Hereinafter, embodiments of the disclosure will be described in detailwith reference to accompanying drawings so that those skilled in the artcan easily replicate with the embodiments. However, the embodiments mayhave various modifications, and the disclosure is not limited thereto.

In the following description, when a predetermined part “includes” apredetermined element, the predetermined part does not exclude otherelements, but may further include other components unless otherwiseindicated.

The thickness and size of each layer shown in the drawings may beexaggerated, omitted or schematically drawn for the purpose ofconvenience or clarity. In addition, the size of elements does notutterly reflect an actual size. The same reference numbers will beassigned the same elements throughout the drawings.

In the description of the embodiments, it will be understood that, whena layer, a film, a region, or a plate is referred to as being “on”another layer, another film, another region, or another plate, it can be“directly” on the other layer, film, region, plate, or one or moreintervening layers may also be present. Meanwhile, it will be understoodthat, when a layer, a film, a region, or a plate is referred to as being“directly on” another layer, another film, another region, or anotherplate, any intervening layer is not present.

The disclosure provides a printed circuit board, in which a conventionalNi surface treatment layer may be omitted by forming a surface treatmentlayer using a removable film-type material and an additional seed layer,and a portion of the top surface of the circuit pattern may be removedtogether with the seed layer when the seed layer is removed.

FIG. 2 is a sectional view showing the structure of a printed circuitboard according to the first embodiment of the disclosure. FIG. 3 is asectional view showing the circuit pattern of FIG. 2 in detail.

Referring to FIGS. 2 and 3 , a printed circuit board 100 includes aninsulating layer 110, a plating seed layer 120, a circuit pattern 130,and a surface treatment layer 140.

The insulating layer 110 may mean a support substrate of the printedcircuit board 100 having a single circuit pattern, and mean aninsulating layer area having one circuit pattern 130 in a printedcircuit board having a plurality of lamination structures.

When the insulating layer 110 means one insulating layer constitutingthe plural lamination structures, a plurality of circuit patterns may becontinuously formed on top and bottom surfaces of the insulating layer110.

The insulating layer 110 may constitute an insulating plate, and mayinclude a thermosetting or thermoplastic polymeric substrate, a ceramicsubstrate, an organic-inorganic composite substrate, or a glass fiberimpregnated substrate. If the insulating layer 110 includes thepolymeric resin, the insulating layer may include epoxy insulatingresin, or may include polyimide based resin.

The insulating layer 110 is formed thereon with the circuit pattern 130.

Preferably, the plating seed layer 120 to be used when the circuitpattern 130 is formed is formed between the insulating layer 110 and thecircuit pattern 130.

The top and bottom surfaces of the plating seed layer 120 may have equalwidths.

Then, the circuit pattern 130 is formed on the plating seed layer 120.

Differently from the plating seed layer 120, the circuit pattern 130 maybe formed in a shape in which the top and bottom surfaces thereof havemutually different widths. In this case, the width of the bottom surfaceof the circuit pattern 130 may be equal to the width of the top surfaceor the bottom surface of the plating seed layer 120, and the width ofthe top surface of the circuit pattern 130 may be narrower than that ofthe bottom surface of the circuit pattern 130.

The plating seed layer 120 and the circuit pattern 130 may be formed ofmetal including copper (Cu) and having electrical conductivity.

The circuit pattern 130 may be formed through an additive process, asubtractive process, a modified semi-additive process (MSAP), or asemi-additive process (SAP), which is a typical process of fabricating aprinted circuit board, and the details thereof will be omitted.

Although drawings show that a single circuit pattern 130 is formed onthe insulating layer 110, a plurality of circuit patterns 130 may beformed on at least one of the top and bottom surfaces of the insulatinglayer 110 while being spaced apart from each other.

Hereinafter, the circuit pattern 130 will be described in more detailwith reference to FIG. 3 . The circuit pattern 130 includes a first part131 formed on the plating seed layer 120 to have a bottom surface makingcontact with the top surface of the plating seed layer 120, and a secondpart 132 formed on the first part 131 to have at least a portion of atop surface making contact with the bottom surface of the surfacetreatment layer 140.

Although the circuit pattern 130 includes the first part 131 and thesecond part 132, the first and second parts 131 and 132 are providedonly for the purpose of explaining the shape of the circuit pattern 130.Actually, the first and second parts 131 and 132 may be integrated witheach other as one component.

The bottom surface of the first part 131 of the circuit pattern 130directly makes contact with the top surface of the plating seed layer120.

In this case, the first part 131 of the circuit pattern 130 may have ashape in which the top and bottom surfaces of the first part 131 haveequal widths.

In addition, the second part 132 of the circuit pattern 130 has mutuallydifferent widths at the bottom and top surfaces thereof.

In other words, in the second part 132 of the circuit pattern 130, thewidth of the top surface is narrower than that of the bottom surface.Accordingly, the lateral side of the second part 132 is formed with apredetermined curvature lengthwise.

In this case, the second part 132 of the circuit pattern 130 may includea first lateral side having a first curvature and a second lateral sidehaving a second curvature. In addition, the first curvature of the firstlateral side may be substantially equal to the second curvature of thesecond lateral side.

Therefore, the circuit pattern 130 has left and right lateral sides.Each of the left and right lateral sides includes a first portionsubstantially perpendicular to a main surface and a second portionextending from the first portion and including a curved surface having apredetermined curvature.

The surface treatment layer 140 is formed on the circuit pattern 130 forthe surface treatment of the circuit pattern 130.

The surface treatment layer 140 may be formed of metal including gold(Au) or the alloy including Au.

When the surface treatment layer 140 is formed of the alloy includingAu, the surface treatment layer 140 may be formed of the Au alloyincluding cobalt (Co). In this case, the surface treatment layer 140 isformed through the electrolytic plating.

Preferably, the surface treatment layer 140 is formed by performing theelectroplating with respect to the plating seed layer 120 that is thesame as the plating seed layer used when the circuit pattern 130 isformed.

The surface treatment layer 140 is formed on the circuit pattern 130.Accordingly, the bottom surface of the surface treatment layer 140directly makes contact with the top surface of the circuit pattern 130.

In this case, the surface treatment layer 140 includes the bottomsurface having the width wider than that of the top surface of thecircuit pattern 130.

Accordingly, the bottom surface of the surface treatment layer 140includes a first bottom surface directly making contact with the topsurface of the circuit pattern 130 and a second bottom surface that doesnot make contact with the top surface of the circuit pattern 130.

In this case, the first bottom surface of the surface treatment layer140 may be the central area of the bottom surface of the surfacetreatment layer 140, and second bottom surfaces of the surface treatmentlayer 140 may be left and right areas of the surface treatment layer140.

In addition, the surface treatment layer 140 may have a shape in whichthe width of the top surface is equal to that of the bottom surface.

Meanwhile, the top and bottom surfaces of the surface treatment layer140 may have widths narrower than that of the bottom surface of thecircuit pattern 130.

Accordingly, as shown in FIG. 2 , the surface treatment layer 140 has aneave structure of protruding outward from the upper lateral side of thecircuit pattern 130.

As described above, according to the disclosure, the surface treatmentlayer 140 including Au is formed using the plating seed layer 120 usedwhen the circuit pattern 130 is formed, the nickel (Ni) surfacetreatment layer serving as the seed layer of the gold (Au) surfacetreatment layer may be removed

In addition, as described above, according to the disclosure, theconventional nickel (Ni) surface treatment layer is omitted, and thesurface treatment layer 140 including gold (Au) is formed directly onthe circuit pattern 130, thereby increasing the electrical conductivity,and reducing the electrical resistance. Accordingly, the RFcharacteristic may be improved.

In addition, as described above, according to the disclosure, thesurface treatment layer 140 formed on the circuit pattern 130 has aneave structure of protruding outward from the upper lateral side of thecircuit pattern 130, so that the mounting area of the components mountedon the circuit pattern may be increased. Accordingly, the reliability ofa customer may be improved.

Hereinafter, the relationship between the circuit pattern 130 and thesurface treatment layer 140 will be described in more detail.

Referring to FIG. 2 , the circuit pattern 130 has the top surface andthe bottom surface having widths different from each other. In thiscase, the bottom surface of the circuit pattern 130 has a first widthW1, and the top surface of the circuit pattern 130 has the second widthW2 narrower than the first width W1.

Accordingly, the bottom surface of the circuit pattern 130 includes asecond area vertically overlapped with the top surface of the circuitpattern 130, and a first area that is not overlapped with the topsurface of the circuit pattern 130.

In addition, the surface treatment layer 140 is formed on the circuitpattern 130, and the top surface and the bottom surface of the surfacetreatment layer 140 have equal third widths W3.

In this case, the third width W3 is narrower than the first width W1 andwider than the second width W2.

Accordingly, the bottom surface of the surface treatment layer 140includes a contact area making contact with the top surface of thecircuit pattern 130 and a non-contact area that protrudes outward of thetop surface of the circuit pattern 130 beyond the contact area and doesnot make contact with the top surface of the circuit pattern 130.

In this case, the bottom surface of the circuit pattern 130 may have awidth wider than that of the top surface of the circuit pattern 130 by afourth width W4.

That is to say, the first area of the circuit pattern 130 may have thefourth width W4.

In this case, the first area of the circuit pattern 130 is partiallyoverlapped with the non-contact area of the surface treatment layer 140.

In other words, the first area of the circuit pattern 130 includes athird area that is not vertically overlapped with the non-contact areaof the surface treatment layer 140 and has a fifth width W5, and afourth area that is vertically overlapped with the non-contact area ofthe surface treatment layer 140 and has a sixth width W6.

In this case, preferably, the fifth width W5 of the third area is widerthan the sixth width W6 of the fourth area.

More preferably, the ratio of the fifth width W5 to the sixth width W6is in the range of 1.5 to 4.0.

In other words, when the ratio of the fifth width W5 to the sixth widthW6 is less than 1.5, the non-contact area of the surface treatment layer140 has a wider area. In this case, the non-contact area of the surfacetreatment layer 140 protruding outward of the top surface of the circuitpattern 130 has an unstable structure, so that the non-contact area maybe collapsed, thereby causing the electrical short.

In addition, when the ratio of the fifth width W5 to the sixth width W6is more than 4.0, the non-contact area of the surface treatment layer140 has a narrower width. In this case, as the entire width of thesurface treatment layer 140 is narrowed, the mounting area may benarrowed.

Therefore, according to the disclosure, when the surface treatment layer140 having the eave structure is formed as described above, the ratio ofthe fifth width W5 to the sixth width W6 satisfies the range of 1.5 to4.0. In this case, the fifth width W5 is wider than the sixth width W6,so that the fifth width W5 has a value ranging from 1.5 to 4 times thatof the sixth width W6.

Hereinafter, a method of fabricating the printed circuit board shown inFIG. 2 will be described in detail with reference to FIGS. 4 to 11 .

FIGS. 4 to 11 are sectional views showing the method of fabricating theprinted circuit board of FIG. 2 in process sequence.

Referring to FIG. 4 , after preparing the insulating layer 110, theplating seed layer 120 is formed on the prepared insulating layer 110.

The plating seed layer 120 may be formed by performing electrolessplating with respect to the insulating layer 110 using metal includingCu.

The insulating layer 110 may include a thermosetting or thermoplasticpolymeric substrate, a ceramic substrate, an organic-inorganic compositesubstrate, or a glass fiber impregnated substrate. If the insulatinglayer 110 includes the polymeric resin, the insulating layer 110 mayinclude epoxy insulating resin, or may include polyimide based resin.

The plating seed layer 120 may be formed by performing typical copperclad laminate (CCL) instead of the electroless plating with respect tothe surface of the insulating layer 110.

In this case, when the plating seed layer 120 is formed through theelectroless plating, surface roughness is applied to the top surface ofthe insulating layer 110, so that the electroless plating may besmoothly performed.

The electroless plating scheme may be performed in the sequence of adegreasing process, a soft etching process, a pre-catalyst process, acatalyst treatment process, an accelerator process, an electrolessplating process, and an anti-oxidation treatment process. In addition,the plating seed layer 120 may be formed by sputtering metallicparticles using plasma.

In this case, before forming the plating seed layer 120 through theplating process, a desmear process of removing smears from the surfaceof the insulating layer 110 may be additionally performed. The desmearprocess is performed to enhance plating power for the formation of theplating seed layer 120 by applying surface roughness onto the surface ofthe insulating layer 11.

Thereafter, referring to FIG. 5 , a first mask 125 is formed on theplating seed layer 120. In this case, the first mask 125 may include adry film.

In this case, the first mask 125 has an opening a to expose at least aportion of the top surface of the plating seed layer 120.

In this case, the top surface of the plating seed layer 120 exposed bythe opening a of the first mask 125 corresponds to an area for thecircuit pattern 130.

In other words, the first mask 125 having the opening a to expose thearea for the circuit pattern 130 in the top surface of the plating seedlayer 120 is formed on the plating seed layer 120.

In this case, the first mask 125 may be formed to cover the whole topsurface of the plating seed layer 120. Accordingly, the opening a may beformed by removing a portion of an area of the plating seed layer 120for the formation of the circuit pattern 130.

Next, referring to FIG. 6 , the circuit pattern 130 is formed on theplating seed layer 120 so that the circuit pattern 130 is filled in atleast a portion of the opening a of the first mask 125.

The circuit pattern 130 may be formed while being filled in the at leasta portion of the opening a of the first mask 125 by performingelectroplating with respect to the plating seed layer 120 serving as aseed layer using a conductive material, preferably, the alloy includingCu.

Next, referring to FIG. 7 , the first mask 125 is removed from theplating seed layer 120.

In this case, after the first mask 125 has been removed, the residues ofthe first mask 125 may remain on the surface of the plating seed layer120. Accordingly, an additional process of removing the residues of thefirst mask 125 may be performed.

Then, referring to FIG. 8 , a second mask 135 is formed on the platingseed layer 120.

In this case, preferably, the second mask 135 may include a dry filmhaving strong heat resistance and an easy removable property.

The second mask 135 includes an opening b to expose the top surface ofthe circuit pattern 130.

In this case, the opening b of the second mask 135 is formed with awidth narrower than that of the top surface of the circuit pattern 130.

Accordingly, at least a portion of the top surface of the circuitpattern 130 is covered by the second mask 135. Preferably, the centralarea of the top surface of the circuit pattern 130 is exposed to theoutside by the opening b of the second mask 135, and the edge areas ofthe top surface of the circuit pattern 130 is covered by the second mask135.

Next, referring to FIG. 9 , the surface treatment layer 140 is formed onthe circuit pattern 130 by employing both of the plating seed layer 120and the circuit pattern 130 as a seed layer.

In this case, the surface treatment layer 140 is formed with a widthequal to that of the opening b of the second mask 135.

The surface treatment layer 140 may be formed of metal including onlygold (Au) or the alloy including Au.

When the surface treatment layer 140 is formed of the alloy includingAu, the surface treatment layer 140 may be formed of the Au alloyincluding Co. In this case, the surface treatment layer 140 may beformed through the electroless plating.

Preferably, the surface treatment layer 140 is formed by performing theelectroplating with respect to the plating seed layer 120 which is thesame as a plating seed layer used when the circuit pattern 130 isformed. In other words, the surface treatment layer 140 is formedthrough the electroplating as the plating seed layer 120 is connectedwith the circuit pattern 130 so that a short occurs between the platingseed layer 120 and the circuit pattern 130.

The surface treatment layer 140 is formed on the circuit pattern 130 sothat the bottom surface of the surface treatment layer 140 directlymakes contact with the top surface of the circuit pattern 130.

In this case, the surface treatment layer 140, which exists before theplating seed layer 120 is removed, includes top and bottom surfaceshaving widths narrower than that of the top surface of the circuitpattern 130.

Accordingly, the top surface of the circuit pattern 130 includes a partthat makes contact with the surface treatment layer 140 and a part thatdoes not make contact with the surface treatment layer 140.

Next, referring to FIG. 10 , the second mask 135 formed on the platingseed layer 120 is removed.

In this case, if the second mask 135 is removed similarly to the processof removing the first mask 125, an additional process may be performedto remove the residues of the second mask 135 remaining on the platingseed layer 120.

Thereafter, referring to FIG. 11 , a process of removing a portion ofthe plating seed layer 120, which is formed on the insulating layer 110and has no the circuit pattern 130, is performed.

In other words, after the second mask 135 has been removed, the processof removing the portion of the plating seed layer 120 formed on theinsulating layer 110 is performed. In this case, when the process ofremoving the plating seed layer 120 is performed, a portion of theplating seed layer 120 which is formed under the circuit pattern 130 isnot removed due to the circuit pattern 130, but only the portion of theplating seed layer 120 having no circuit pattern 130 is selectivelyremoved.

In this case, edge areas of the top surface of the circuit pattern 130have no the surface treatment layer 140. Accordingly, when the processof removing the portion of the plating seed layer 120, which is formedon the insulating layer 110 and has no the circuit pattern 130, isperformed, the edge areas of the top surface of the circuit pattern 130,which are not covered by the surface treatment layer 140, are alsoremoved.

In this case, only a portion of the top surface of the circuit pattern130, which is not covered by the surface treatment layer 140, isremoved.

Accordingly, upper lateral sides of the circuit pattern 130 are removedwith a predetermined curvature differently from the lower portion of thecircuit pattern 130.

Therefore, the bottom surface of the surface treatment layer 140 mayhave the width wider than that of the top surface of the circuit pattern130.

In addition, due to the process of removing the above plating seed layer120, the bottom surface of the surface treatment layer 140 includes afirst bottom surface directly making contact with the top surface of thecircuit pattern 130 and second bottoms surface that does not makecontact with the top surface of the circuit pattern 130.

In this case, the first bottom surface of the surface treatment layer140 may be the central area of the bottom surface of the surfacetreatment layer 140, and the second bottom surfaces of the surfacetreatment layer 140 may be left and right areas of the surface treatmentlayer 140.

Meanwhile, the top and bottom surfaces of the surface treatment layer140 may have the widths narrower than the width of the bottom surface ofthe circuit pattern 130.

In other words, as the edge areas of the upper portion of the circuitpattern 130 are removed in the process of removing the plating seedlayer 120, the circuit pattern 130 may be divided into the first part131 and the second part 132 as described above.

The bottom surface of the first part 131 of the circuit pattern 130directly makes contact with the top surface of the plating seed layer120.

In this case, the first part 131 of the circuit pattern 130 has a shapein which the top surface and the bottom surface of the first part 131have equal widths.

In addition, the second part 132 of the circuit pattern 130 has a shapein which the top surface and the bottom surface have mutually differentwidths.

In other words, in the second part 132 of the circuit pattern 130, thewidth of the top surface is narrower than that of the bottom surface.Accordingly, the lateral sides of the second part 132 are formed with apredetermined curvature lengthwise.

In this case, the second part 132 of the circuit pattern 130 may includethe first lateral side having the first curvature and the second lateralside having the second curvature. In addition, the first curvature ofthe first lateral side may be substantially equal to the secondcurvature of the second lateral side.

Therefore, the circuit pattern 130 has left and right lateral sides, andeach of the left and right lateral sides includes a first portionsubstantially perpendicular to a main surface and a second portionextending from the first portion and including a curved surface having apredetermined curvature.

Accordingly, as shown in FIG. 2 , the surface treatment layer 140 hasthe eave structure of protruding outward from the upper lateral side ofthe circuit pattern 130.

As described above, according to the disclosure, the surface treatmentlayer 140 including Au is formed by utilizing the plating seed layer 120used when the circuit pattern 130 is formed, so that the nickel (Ni)surface treatment layer serving as the seed layer for the gold (Au)surface treatment layer may be omitted

In addition, as described above, according to the disclosure, theconventional nickel (Ni) surface treatment layer is omitted, and thesurface treatment layer 140 including gold (Au) is formed directly onthe circuit pattern 130, thereby increasing the electrical conductivity,and reducing the electrical resistance. Accordingly, the RFcharacteristic may be improved.

In addition, as described above, according to the disclosure, thesurface treatment layer 140 formed on the circuit pattern 130 has theeave structure of protruding outward from the upper lateral side of thecircuit pattern 130, so that the mounting area of the components mountedon the circuit pattern may be increased. Accordingly, the reliability ofa customer may be improved.

FIG. 12 is a sectional view showing the structure of a printed circuitboard according to the second embodiment of the disclosure.

Referring to FIG. 12 , a printed circuit board 200 includes aninsulating layer 210, a plating seed layer 220, a circuit pattern 230,and a surface treatment layer 240.

The insulating layer 210 may mean a support substrate of the printedcircuit board 100 having a single circuit pattern, and mean aninsulating layer area having one circuit pattern 230 in a printedcircuit board having a plurality of lamination structures.

The insulating layer 210 may constitute an insulating plate, and mayinclude a thermosetting or thermoplastic polymeric substrate, a ceramicsubstrate, an organic-inorganic composite substrate, or a glass fiberimpregnated substrate. If the insulating layer 210 includes thepolymeric resin, the insulating layer 210 may include epoxy insulatingresin, or may include polyimide based resin.

The circuit pattern 230 is formed on the insulating layer 210.

Preferably, the plating seed layer 120 for the formation of the circuitpattern 230 is formed between the insulating layer 210 and the circuitpattern 230.

The top and bottom surfaces of the plating seed layer 220 may have equalwidths.

In addition, the circuit pattern 230 is formed on the plating seed layer220.

Differently from the plating seed layer 220, the circuit pattern 230 mayhave a shape in which the top and bottom surfaces thereof have mutuallydifferent widths. In this case, the width of the bottom surface of thecircuit pattern 230 may be equal to that of the top surface or thebottom surface of the plating seed layer 220. The width of the topsurface of the circuit pattern 230 may be narrower than that of thebottom surface of the circuit pattern 230.

The plating seed layer 220 and the circuit pattern 230 are formed ofmetal including Cu and having electrical conductivity.

The circuit pattern 230 may be formed through an additive process, asubtractive process, a modified semi-additive process (MSAP), or asemi-additive process (SAP), which is a typical process of fabricating aprinted circuit board, and the details thereof will be omitted.

Although drawings show that a single circuit pattern 230 is formed onthe insulating layer 210, a plurality of circuit patterns 230 may beformed on at least one of the top surface and the bottom surface of theinsulating layer 210 while being spaced apart from each other by apredetermined distance.

In this case, the circuit pattern 230 may have a shape similar to thatof the circuit pattern 130 according to the first embodiment. Althoughboth lateral sides of the circuit pattern 130 according to the firstembodiment have a predetermined curvature, the circuit pattern 230according to the second embodiment has a predetermined curvature only atan upper right lateral side thereof.

In other words, the left lateral side of the circuit pattern 230 issubstantially perpendicular to the bottom surface of the circuit pattern230, and the right lateral side of the circuit pattern 230 has a portionsubstantially perpendicular to the bottom surface of the circuit pattern230 and a curved surface portion extending from the perpendicularportion and having a predetermined curvature.

The surface treatment layer 240 is formed on the circuit pattern 230 toperform the surface treatment of the circuit pattern 230.

The surface treatment layer 240 may be formed of metal including only Auor the alloy including Au.

When the surface treatment layer 240 is formed of the alloy includingAu, the surface treatment layer 240 may be formed of the Au alloyincluding Co. In this case, the surface treatment layer 240 is formedthrough electroless plating.

Preferably, the surface treatment layer 240 is formed by performing theelectroplating with respect to the plating seed layer 220 which is thesame as the plating seed layer used when the circuit pattern 230 isformed.

The surface treatment layer 240 is formed on the circuit pattern 230, sothat the bottom surface of the surface treatment layer 240 directlymakes contact with the top surface of the circuit pattern 230.

In this case, the surface treatment layer 240 includes the bottomsurface having a width wider than that of the top surface of the circuitpattern 230.

Accordingly, the bottom surface of the surface treatment layer 240includes a first bottom surface that directly makes contact with the topsurface of the circuit pattern 230 and a second bottom surface that doesnot make contact with the top surface of the circuit pattern 230.

In this case, the first bottom surface of the surface treatment layer240 may include the central area and a left area of the bottom surfaceof the surface treatment layer 240, and the second bottom surface of thesurface treatment layer 240 may include a right area of the surfacetreatment layer 240.

In addition, the surface treatment layer 240 may have a shape in whichthe top and bottom surfaces thereof have equal widths.

Meanwhile, both of the top and bottom surfaces of the surface treatmentlayer 240 may have widths narrower than that of the bottom surface ofthe circuit pattern 230.

Accordingly, differently from that of the first embodiment, the surfacetreatment layer 240 according to the second embodiment has an eavestructure of protruding outward from only the upper lateral side of thecircuit pattern 230.

As described above, according to the disclosure, the surface treatmentlayer 240 including Au is formed utilizing the plating seed layer 220used when the circuit pattern 230 is formed, so that the nickel (Ni)surface treatment layer serving as the seed layer for the gold (Au)surface treatment layer may be omitted.

In addition, as described above, according to the disclosure, theconventional nickel (Ni) surface treatment layer is omitted, and thesurface treatment layer 140 including gold (Au) is formed directly onthe circuit pattern 130, thereby increasing the electrical conductivity,and reducing the electrical resistance. Accordingly, the RFcharacteristic may be improved.

In addition, as described above, according to the disclosure, thesurface treatment layer 240 formed on the circuit pattern 230 has aneave structure of protruding outward from the upper right lateral sideof the circuit pattern 230, so that the mounting area of the componentsmounted on the circuit pattern 230 may be increased. Accordingly, thereliability of a customer may be improved.

Hereinafter, a method of fabricating the printed circuit board shown inFIG. 12 will be described with reference to FIGS. 13 to 15 .

FIGS. 13 to 15 are sectional views showing the method of fabricating theprinted circuit board shown in FIG. 12 in process sequence.

First, referring to FIG. 13 , after preparing the insulating layer 210,the plating seed layer 220 is formed on the prepared insulating layer210.

The plating seed layer 220 may be formed by performing electrolessplating with respect to the insulating layer 110 using metal includingCu.

The insulating layer 210 may include a thermosetting or thermoplasticpolymeric substrate, a ceramic substrate, an organic-inorganic compositesubstrate, or a glass fiber impregnated substrate. If the insulatinglayer 210 includes the polymeric resin, the insulating layer 210 mayinclude epoxy insulating resin, or may include polyimide based resin.

Next, the circuit pattern 230 is formed by performing electroplatingwith respect to the plating seed layer 220 serving as a seed layer usinga conductive material, preferably, the alloy including Cu.

Thereafter, a mask 225 is formed on the plating seed layer 220.

In this case, preferably, the mask 225 may include a dry film havingstrong heat resistance and an easy removable property.

The mask 225 includes an opening B to expose the top surface of thecircuit pattern 230.

The width of the opening B of the mask 225 is narrower than that of thetop surface of the circuit pattern 230.

Accordingly, at least a portion of the top surface of the circuitpattern 230 is covered by the mask 225. Preferably, the central area andthe left area of the top surface of the circuit pattern 230 are exposedto the outside by the opening B of the mask 225, and the right edge areaof the top surface of the circuit pattern 230 is covered by the mask225.

Next, referring to FIG. 14 , the surface treatment layer 240 is formedon the circuit pattern 230 by employing the plating seed layer 220 andthe circuit pattern 230 as a seed layer.

In this case, the surface treatment layer 240 has a width equal to thatof the opening B of the mask 225.

The surface treatment layer 240 may be formed of metal including only Auor the alloy including Au.

When the surface treatment layer 240 is formed of the alloy includingAu, the surface treatment layer 240 may be formed of the Au alloyincluding Co. In this case, the surface treatment layer 240 is formedthrough electroless plating.

Preferably, the surface treatment layer 240 is formed by performing theelectroplating with respect to the plating seed layer 220 which is thesame as the plating seed layer used when the circuit pattern 230 isformed. In other words, the surface treatment layer 240 is formedthrough the electroplating as the plating seed layer 220 is connectedwith the circuit pattern 230 so that a short occurs between the platingseed layer 220 and the circuit pattern 230.

The surface treatment layer 240 is formed on the circuit pattern 230 sothat the bottom surface of the surface treatment layer 240 directlymakes contact with the top surface of the circuit pattern 230.

In this case, the surface treatment layer 240, which exists before theplating seed layer 220 is removed, includes top and bottom surfaceshaving a width narrower than that of the top surface of the circuitpattern 230.

Accordingly, the top surface of the circuit pattern 230 includes aportion, which makes contact with the surface treatment layer 240, and aportion which does not make contact with the surface treatment layer240.

Thereafter, referring to FIG. 15 , the mask 225 is removed from theplating seed layer 220.

Then, a process of removing a portion of the plating seed layer 220,which is formed on the insulating layer 210 and has no circuit pattern230, is performed.

In other words, after the mask 225 has been removed, the process ofremoving the portion of the plating seed layer 220, which is formed onthe insulating layer 210 and has no circuit pattern 230, is performed.In this case, when the process of removing the portion of the platingseed layer 220, which is formed on the insulating layer 210 and has nocircuit pattern 230, is performed, a portion of the plating seed layer120 which is formed under the circuit pattern 130 is not removed due tothe circuit pattern 130, but only the portion of the plating seed layer220 having no circuit pattern 130 is selectively removed.

In this case, a right edge area of the top surface of the circuitpattern 230 has no surface treatment layer 240. Accordingly, when theprocess of removing the plating seed layer 220 is performed, the rightedge area of the top surface of the circuit pattern 230, which are notcovered by the surface treatment layer 240, are also removed.

In this case, only the upper portion of the circuit pattern 230, whichis not covered by the surface treatment layer 240, is removed.

Accordingly, the upper right portion of the circuit pattern 230, whichis not covered by the surface treatment layer 240, has a lateral sidewith a predetermined curvature differently from that of the lowerportion of the circuit pattern 230.

Accordingly, the bottom surface of the surface treatment layer 240 has awidth wider than that of the top surface of the circuit pattern 230.

The bottom surface of the surface treatment layer 240 includes a firstbottom surface, which directly makes contact with the top surface of thecircuit pattern 230, and a second bottom surface which does not makecontact with the top surface of the circuit pattern 230 due to theprocess of removing the plating seed layer 220.

In this case, the first bottom surfaces of the surface treatment layer240 may include the central area and a left area of the bottom surfaceof the surface treatment layer 240, and the second bottom surface of thesurface treatment layer 240 may include the right area of the surfacetreatment layer 240.

Meanwhile, the top and bottom surfaces of the surface treatment layer240 may have widths narrower than that of the bottom surface of thecircuit pattern 230.

In addition, the upper right lateral side of the circuit pattern 230 isformed with a predetermined curvature lengthwise.

Accordingly, as shown in FIG. 12 , the surface treatment layer 240 hasan eave structure of protruding outward from the upper right lateralside of the circuit pattern 230.

As described above, according to the disclosure, the surface treatmentlayer 240 including Au is formed using the plating seed layer 220 usedwhen the circuit pattern 230 is formed, so that the nickel (Ni) surfacetreatment layer serving as the seed layer for the gold (Au) surfacetreatment layer may be omitted.

In addition, as described above, according to the disclosure, theconventional nickel (Ni) surface treatment layer is omitted, and thesurface treatment layer 140 including gold (Au) is formed directly onthe circuit pattern 130, thereby increasing the electrical conductivity,and reducing the electrical resistance. Accordingly, the RFcharacteristic may be improved.

In addition, as described above, according to the disclosure, thesurface treatment layer 240 formed on the circuit pattern 230 has aneave structure of protruding outward from the upper lateral side of thecircuit pattern 230, so that the mounting area of the components mountedon the circuit pattern may be increased. Accordingly, the reliability ofa customer may be improved.

FIG. 16 is a sectional view showing the structure of a printed circuitboard according to the third embodiment of the disclosure.

Referring to FIG. 16 , a printed circuit board 300 includes aninsulating layer 310, a plating seed layer 320, a circuit pattern 330,and a surface treatment layer 340.

In this case, since the insulating layer 310 and the plating seed layer320 are the same as those of the first embodiment and the secondembodiment, the details thereof will be omitted.

In addition, the circuit pattern 230 according to the second embodimentincludes an upper right lateral side having a predetermined curvature.

However, the circuit pattern 330 according to the third embodiment ofthe disclosure has an upper left lateral side having a predeterminedcurvature, and a right lateral side is formed to be substantiallyperpendicular to the bottom surface.

FIG. 17 is a sectional view showing a printed circuit board 400according to a fourth embodiment of the disclosure.

Referring to FIG. 17 , the printed circuit board 400 includes aninsulating layer 410, a plating seed layer 420, a circuit pattern 430, asurface treatment layer 440, and a protective layer 450.

In this case, since the insulating layer 410, the plating seed layer420, the circuit pattern 430, and the surface treatment layer 440 arethe same as those of the printed circuit board according to the firstembodiment of the disclosure shown in FIG. 2 , the details thereof willbe omitted.

The printed circuit board 400 according to the fourth embodiment furtherincludes a protective layer 450 formed on the insulating layer 410 tocover the surface of the insulating layer 410, the lateral side of theplating seed layer 420, the lateral side of the circuit pattern 430, anda portion of the top surface of the surface treatment layer 440.

The protective layer 450 protrudes from the top surface of the surfacetreatment layer 440 by a predetermined height.

The protective layer 450 may include solder resist, protect the surfaceof the insulating layer 410, and at least a portion of the top surfaceof the surface treatment layer 240 of the circuit pattern formed on theinsulating layer 410.

The protective layer 450 according to the fourth embodiment covers theexposed entire surface of the insulating layer 410.

FIG. 18 is a sectional view showing a printed circuit board according toa fifth embodiment.

Referring to FIG. 18 , a printed circuit board 500 includes aninsulating layer 510, a plating seed layer 520, a circuit pattern 530, asurface treatment layer 540, and a protective layer 550.

Since the insulating layer 510, the plating seed layer 520, the circuitpattern 530, and the surface treatment layer 540 are the same as thoseof the printed circuit board according to the first embodiment of thedisclosure shown in FIG. 2 , the details thereof will be omitted.

The printed circuit board 500 according to the fifth embodiment furtherincludes the protective layer 550 formed on the insulating layer 510 tocover a portion of the surface of the insulating layer 510.

The protective layer 550 is formed on the insulating layer 510 andspaced apart from the circuit pattern 530 by a predetermined distance.

The protective layer 550 may include solder resist, protect the surfaceof the insulating layer 510, and expose the top surface of the surfacetreatment layer 540 of the circuit pattern formed on the insulatinglayer 510 and a portion of the surface of the insulating layer 510.

According to the embodiment of the disclosure, the surface treatmentlayer is formed by utilizing a removable film-type material and aplating seed layer used in the circuit pattern, so that the electrolyticsurface treatment and the electroless surface treatment may beselectively used without the limitation on the design.

According to the embodiment of the disclosure, the surface treatmentlayer including Au is formed using the plating seed layer used when thecircuit pattern is formed, so that a Ni surface treatment layer servingas a seed layer for the Au surface treatment layer according to therelated art may be omitted. Accordingly, the thickness of a product maybe reduced, and product cost may be reduced due to the omission of theNi surface treatment layer.

In addition, according to the disclosure, the conventional nickel (Ni)surface treatment layer is omitted, and the surface treatment layer 140including gold (Au) is formed directly on the circuit pattern 130,thereby increasing the electrical conductivity, and reducing theelectrical resistance. Accordingly, the RF characteristic may beimproved.

Further, according to the embodiment of the disclosure, the surfacetreatment layer formed on the circuit pattern has an eave structure ofprotruding outward from the upper lateral side of the circuit pattern,so that the mounting area of the components mounted on the circuitpattern may be increased. Accordingly, the reliability of a customer maybe improved.

Any reference in this specification to “one embodiment,” “anembodiment,” “example embodiment,” etc., means that a particularfeature, structure, or characteristic described in connection with theembodiment is included in at least one embodiment of the invention. Theappearances of such phrases in various places in the specification arenot necessarily all referring to the same embodiment. Further, when aparticular feature, structure, or characteristic is described inconnection with any embodiment, it is submitted that it is within thepurview of one skilled in the art to effect such feature, structure, orcharacteristic in connection with other ones of the embodiments.

Although embodiments have been described with reference to a number ofillustrative embodiments thereof, it should be understood that numerousother modifications and embodiments can be devised by those skilled inthe art that will fall within the spirit and scope of the principles ofthis disclosure. More particularly, various variations and modificationsare possible in the component parts and/or arrangements of the subjectcombination arrangement within the scope of the disclosure, the drawingsand the appended claims. In addition to variations and modifications inthe component parts and/or arrangements, alternative uses will also beapparent to those skilled in the art.

1. A circuit board comprising: an insulating layer; a first metal layerdisposed on the insulating layer; and a second metal layer disposed onthe first metal layer, wherein the first metal layer includes: an uppersurface in contact with the second metal layer, a lower surface facingthe insulating layer, and a side surface disposed between the uppersurface and the lower surface.